UCD use cases

[Guy Rixon]

An additional case:

I have a heap of data expressing modelled and observed values for a handful of
quantities; celestial coords and proper motions would do as an example.  I
want to read out all the modelled versions of one of these quantities and
compare them to assess the spread of the models.  Then I want to do the same
with the observations.  What do I look for?

On Tue, 21 Oct 2003, Roy Williams wrote:

> Please find below some possible use cases for UCD.
>
> -- How do the different proposed UCD/DM schemes help with these cases?
>
> -- What does the query look like in each case, and how would that query be
> coded?
>
> -- Can you supply additional use cases? Please try to stay within the realm
> of the possible here!
>
> -- If you refer to a Data Model, please try to be concrete about
> who/how/example. Please do not simply invoke "the Future IVOA Data Model".
>
> Thank you
> Roy
> --------------------------
>
> (1) Cone search. How to decide which columns are the RA,Dec that was used in
> the search. What frame (B1950, J2000, ...) do these come from? If there are
> columns with ID, what sort of ID is it, and how do I resolve it?
>
> (2) SIAP search. Find the column that contains the URLs where the images
> are. Find out if there are other columns that have RA,Dec of the image
> center.
>
> (3) We have for example a crossmatch service that is clever enough to know
> about error ellipses. How does it get from a table the most sophisticated
> error info that is there: (a) position (b) circular error (c) ellipse error.
>
> (4) We want to compare photometry in two tables covering the same star
> cluster. How do I decide if they share measurements in the same filter? One
> has R band, the other has Halpha. What happens if fluxes are expressed
> differently -- eg number / energy /
> magnitude / luminosity density.
>
> (5) I want distances to stellar objects measured in meters, so I can make a
> 3D display for the children. How do I recognize a redshift (z) value, how do
> I recognize a radial velocity, how do I recognize an actual distance
> measure?
>
> (6) I am looking for supernovae that have both optical and Xray
> measurements. Can I (should I) use UCD to help my search?
>
> (7) How do I find 21cm observations (that may be redshifted), which also
> have polarization information?
>

Guy Rixon 				        gtr at ast.cam.ac.uk
Institute of Astronomy   	                Tel: +44-1223-337542
Madingley Road, Cambridge, UK, CB3 0HA		Fax: +44-1223-337523